As an instrument capable of measuring the circulation of blood/blood circulation movement and a change in hemoglobin inside an organism easily and noninvasively, an instrument has been proposed which measures the inside of an organism by irradiating light beams of wavelengths ranging from visible rays to infrared rays to the organism and detecting light reflected from the organism (for example, JP-A-9-98972 and JP-A-9-149903).
The biological light measuring instrument is applied to clinics and in case the head, for instance, is a subject to be measured, an activated state of hemoglobin change inside a brain and a local internal bleeding inside the brain can be measured and besides, motion, feeling and the highly-graded cerebral function representing thinking that are related to a change in hemoglobin inside the brain can be measured. For example, Eiju Watanabe (MEDIX VOL30) reports that a change in local cerebral blood flow (epileptic focus) during an epileptic fit can be captured by means of a light measuring instrument (optical topography instrument).
In the conventional light measuring instrument, however, a local change in hemoglobin inside the brain is displayed on a two-dimensional plane representative of an arrangement of light irradiators and photodetectors, so that the three-dimensional positional relation between the light irradiator and photodetector and the subject head is not clarified, making it difficult to specify which region of the brain the hemoglobin change occurs in. Accordingly, even in the case of the aforementioned application of measurement results of the epileptic focus to clinics, for instance, a brain site to be cut off through a surgical operation is difficult to specify.